Signaling mirror



Dec. 17, 1946. RQ s. HUNTER SIGNALING MIRROR Filed Aplfil 20, 1945 2Sheets-Sheet 1 lNvENToR P/c/m/eo 5. HUNTER ATTORNEY Dec. 17, 194s. R s,HUNTE'R 2,412,616"

S IGNALING MIRROR Filed April 20, 1945 2 Sheets-Sheet 2 Patented Dec.17, 1946 SIGNALING' MIRROR Richard S. Hunter, Franklin Park, Va.,assignor to United States of America, as represented by the Secretary ofCommerce Application April 20, 1945, Serial No. 589,451

(Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) 5 Claims.

The invention described herein may be manufactured and used by or forthe Government of the United States for governmental purposes withoutthe payment t me of any royalty thereon in accordance with theprovisions of the act of April 30, 1928 (Ch. 460, 45 Stat. L. 467).

My invention relates to heliographic means for sending distress signalsto passing aircraft or watercraft and particularly to one which may bequickly and accurately aimed, and has a relatively wide angular range.

In the accompanying drawings:

Figure 1 is a plan view of my signaling mirror.

Fig. 2 is a cross section on the line 2-2 of Figure l.

Figure 3 is a plan view of a polished metal modication.

Figure 4 is a section on the line 3-3 of Figure 3.

Figure 5 is an enlarged' detail of a portion of Figure 2 showing thearrangement of my lter and retrodirective reflector,

Figure 6 is an enlarged diagrammatic View showing the application of thedevice when signaling an airplane.

In my signaling mirror illustrated in Figures 1 and 2:

A mirror It] made of tempered glass, transparent plastic or the liketransparent refractive material, has an upper surface II anda metallicmirror coating I2, and is provided with a suitable window I3 formed bythe omission of a selected portion of the coating I2. Under the windowI3 is a transparent refractive layer I4, preferably a disk of clearplastic marginally cemented to the mirror, but optically separated fromthe window portion of the mirror. A spacing washer l5 is cementedbetween the disk I4 and a second disk I5 of clear refractive plastic.Within the washer I5 and between the disk I4 and the second disk I6 areconiined a thin, preferably red color filter II having a sightingaperture I8 and a disk I9 provided with a sighting aperture 20. The diskI9 possesses a high-angularty retrodirective reiiecting surface formedby a layer of very small spheres 22 embedded in very thin exiblematerial 2l (see Figure 5).

My device is protected by a suitable casing 23 of plastic or the like,having an inturned marginal ange 24 which engages the mirror and anannular ange 23 which covers and protects the margin of the disk I6.Besides protecting my signaling device from rough handling the casing 23provides an additional means for excluding moisture.

In Figures 3 and 4 there is illustrated a modication in which therefiecting element is a metal plate 3l, provided with a polishedmirrored surface 32 and a window 33. The window 33 is covered by twodisks of transparent light refractive plastic 34 and 35 which areslightly separated as by a marginal layer of cement but are opticallyindependent,

A third disk of transparent plastic material 35 is placed against the-underside of the plate 3l. A filter il and a reflecting disk I9 areplaced within the window 33 and by means of a plurality of rivets 3l thedisks 34, 35 and'36 are rigidly secured to the plate 3l.

The application of my device for signaling is diagrammaticallyillustrated in Figure 6. In this figure are shown by broken lines thedirect rays of the sun from the right which are reected from themirrored surface I2 and also from the upper surface II of the mirror IB.

Accuracy and speed in aiming my mirror are essential to the sending of adistress signal. For the purpose of aiming, certain rays are divertedthrough the window I3 and sighting apertures I8 and 20 to the eye of aperson sending the signal.

For the purpose of illustration, the courses of three arbitrarilyselected rays, designated a, b and c are indicated by heavy broken lines(Figure 6). A portion of the ray b upon striking the upper surface II ofthe mirror is refracted as it passes downwardly and is again refractedas it passes out through the window I3. It is similarly refracted by thelayer I4, and passes through the color filter I'I to one of the tinyspheres 22. Each embedded sphere has the property of reversing thedirection of a ray which strikes it. The retro-reflected ray, colored bypassing twice through the filter Il, is split into two portions uponreaching the upper surface of the layer I4, one portion being reflectedto the right and being lost because it strikes the disk I9. Anotherportion of this colored ray is reflected to the right by the yundersurface of the mirror Ill, within the window I3, and is reecteddownwardly to the right through the sighting apertures I8 and 20 to theeye of the person sending a signal. The ray c follows courses parallelto those of the ray b as far as the upper surface of the disk I4 whereit is reflected downwardly through the sighting openings I8 and 20 alongthe line of the ray b, thus intensifying the brilliance of this ray.Similarly, the ray a follows courses parallel to the rays b and c to thesurface I I of the mirror I0 where it is reflected downwardly to theright and joins the reflected rays b and c, thus further intensifyingthis ray. A plurality of rays following paths parallel to a, b, and calso pass through the apertures I8 and 20 to the eye of a signaler whosees a glowing red spot which appears to him to be in space. The redspot is in reality a virtual red image of the sun diagrammaticallyindicated by the numeral 38 and when he succeeds in aligning thisvirtual image 38 with an aircraft 39, the white light reflected from themirror will be directed upon the craft in the endeavor to attract theattention of the crew. Y y

Similarly, it is possible, if a still brighter red spot is desired, toinsert additional transparent refractive layers in front f theretrodirective surface which will reflect additionalvred rays backthrough the sighting apertures.

Because moisture would interfere with the sighting of my mirror,precautions are taken to seal all external joints both between my mirrorl' and the casing 23 and between the transparent members.

While I have shown and described certain embodiments of my invention, itis to be understood that it is capa-ble of many modifications, changes,therefore in the construction and arrangement may be made withoutdeparting from the spirit and scope of the invention as disclosed in theappended claims, in which it is my intention to claim all noveltyinherent in my invention as broadly as possible in view of the priorart.

What I claim is:

l. A signaling device comprising a mirror provided with a window, atransparent optically separate layer covering said window, a highangularity retrodirective reflective sheet provided with a sightingopening covering said layer and a transparent protecting layer confiningsaid lm against said rst transparent layer.

2. A signaling mirror provided with a window, a transparent refractivelayer mounted over said window, an apertured colored filter and a highangularity retrodirective reective sheet provided with an alignedopening covering said layer, and a second transparent protecting layermarginally united to and confining said sheet against said firsttransparent layer.

3. A signaling device as defined in claim 2 having the first of saidtransparent refractive layers united at its margins to the mirror and tosaid second transparent layer.

4. In a heliographic signaling device comprising a mirror provided witha window, a retrodirective reflecting sheet provided with a sightingaperture, a color lter provided with an aligned aperture and aprotective transparent refractive layer, and a second transparentrefractive layer between said lmirror window and said vsheet confiningbut not optically united to said sheet.

5. A heliographic signaling device comprising an opaque mirror providedwith a window, a retrodirective reflecting sheet provided with asighting aperture and a color filter provided with an aligned sightingaperture within the window of said mirror, a clear transparent diskbeneath said window and extending beyond the margins thereof, twosimilar transparent optically independent disks above said window andmeans for rigidly uniting said disks to said mirror.

RICHARD S. HUNTER.

